Printed circuit boards usually contain a plurality of holes having small diameters (e.g. approximately 1 millimeter or less) that are made conductive, for example, by electroplating or inserting metal eyelets, to electrically connect board layers. Some of the holes on the PCB may be used to accommodate insertion of through-hole component leads. For example, walls of holes for boards with two or more layers can be made conductive and electroplated with electrically conducting material (e.g. copper) to form plated-through holes. These holes may electrically connect the conducting layers of the PCB.
In order to properly provide electrical connections among various chips, chip holders, or other components that may be attached to a PCB, it is important that the PCB holes are drilled with high degree of accuracy and are uniform in their dimensions.
Like reference numerals are used in the drawings to denote like elements and features.